Apparatus and method for handling flexible tubes

ABSTRACT

Apparatus for and a method of handling flexible tubes, for example in the production of a liner for a cargo container to provide a tubular attachment on the liner. A tube  16  in the form of a web of flexible material is drawn over a support  39  mounted on a carrier  29,30 , the support having a greater area than that of the opened-out tube and being tilted to the radial plane (FIG.  2 ) during the drawing action. The support is then moved to the radial plane (FIG.  4 ) so as to stretch the tube  16  in the region of the support whereafter the tube is cut from the web, in the vicinity of the support. The support  39  is moved to a further processing station (FIG.  8 ), carrying the cut off tube  16 , whereat the tube is released from the support  39  by tilting the support once more and withdrawing the support from the tube. The support is then returned to its initial position ready for another cycle of operation.

FIELD OF INVENTION

This invention relates to apparatus for handling a tube of flexibleplasticsmaterial cut from a web of that material. The invention furtherrelates to a method of handling such a tube, for the further processingthereof.

The apparatus and method of this invention are particularly concernedwith the manufacture of container liners and will in the following bedescribed essentially solely in relation to that manufacturing process.It is however to be understood that the invention is not limited to thatmanufacturing process and aspects of the apparatus and method mayequally be used in other processes.

BACKGROUND OF THE INVENTION

Liners for cargo containers, such as ISO box containers, are well-knownand widely used for the bulk transport of flowable products—for examplegranular materials including agricultural produce and chemicals. Suchliners are usually made from plastics sheet material which is pre-formedinto a tube, or from sheet material which is suitably folded andsubsequently is seam-welded to make a tube. End panels for a liner areprovided either by welding the plastics material in an appropriatemanner or by bonding into the tube a separate end panel. Access openingsare provided both for the loading and discharge of the liner, when inuse, and such openings frequently are fitted with access pipes—forexample for the introduction of the product into the liner. Further,suitable arrangements must be made for the suspension of the liner in acontainer.

The manufacture of such a container liner tends to be somewhat labourintensive. Typically, a web of the plastics material is supportedadjacent a work-table and is drawn out over that work-table so that therequired operations may be performed by operators reaching across theliner and using suitable tools, such as thermal welding apparatus. Inview of the width of such a liner, these operations are not very easy toperform in the central region of the liner where, for example an accesspipe must be bonded to the liner, around an access opening formedthrough the material of the liner. A high degree of skill is required toensure the bonding process, such as thermal welding, is carried outefficiently to provide a reliable joint which will not fail in use.

SUMMARY OF THE INVENTION

The present invention stems from research into ways for facilitating thehandling of a plastics material tube which is to form the access pipe ofa completed liner, and so which must be cut from a web of flexibleplastics material and then bonded to a liner, around an openingpre-formed therein. The access pipe may be made of relatively thin-wallplastics material and so is not self-supporting; this leads toparticular difficulties in handling the tube both at the time of cuttinga suitable length from the web and subsequently to shape and bond thetube to the liner, to form the access pipe.

According to one aspect of the present invention, there is thereforeprovided apparatus for handling a tube of flexible plastics materialdrawn and then cut from a web thereof, which apparatus comprises adisc-shaped support having a greater diameter than the internal diameterof the tube and over which the material is drawn, and a carrier for thesupport, in which apparatus the support is mounted on the carrier formovement between a first position where the support lies at an angle toa radial plane of the tube to permit drawing of the tube thereover and asecond position where the support lies substantially in a radial planeof the tube so that the part of the tube in which is located the supportis stretched over the support and so is held thereby.

According to a second and closely related aspect of the presentinvention, there is provided a method of handling a tube of flexibleplastics material using a disc-shaped support having a greater diameterthan the internal diameter of the tube when opened out and beingadjustably mounted on a carrier for movement between a first positionwhere the support lies at an angle to a radial plane of the tube and asecond position where the support lies substantially in a radial planeof the tube, in which method the support is disposed at its firstposition, a length of the tube is drawn over the support from a webthereof, the support is moved to its second position so that the part ofthe tube in which is located the support is stretched over the supportand so is held thereby, and the drawn length of the tube is cut from theweb, adjacent the support.

By using the apparatus of this invention, or performing the method ofthis invention, it becomes possible to handle on an automated basis atube of relatively flexible, or “floppy”, plastics material to form anaccess pipe for a container liner. Despite the nature of the plasticsmaterial, a required length of the tube may be cut from the web and thenbe transferred to a bonding station where the tube is bonded to thematerial of the liner, around an opening pre-formed in the liner,without the need for intervening manual operations.

The handling of the floppy tube is possible in view of the movement ofthe support between its first and second positions—the support shouldhave an effective projected area of no greater than the area of the tube(when opened out into a circular shape) when the support is in its firstposition, but has an effective area greater than the area of the tubewhen the support is in its second position. Thus, the material may bedrawn over the support relatively easily so as to have the supportpositioned within the tube adjacent one end thereof, when the support isin its first position, but the tube is held firmly, in its opened-outconfiguration, when the support is in its second position.

Preferably, the support is moveable to a third position inclined at anangle to the radial plane of the tube and beyond the second positionwith respect to the first position. In this case, the movement of thesupport from the first position may go through the second position tothe third position before finally returning to the second position. Such“over-running” of the support by a few degrees ensures that the materialof the tube is not unduly stretched locally when the support finally isin its second position, and that the support is properly located in thetube, in a radial plane, at the time the tube is cut from the web.

Conveniently, the carrier is mounted on a sub-frame, arranged formovement of the support from a loading position where the tube is drawnover the support, to a discharge position where a cut length of tube issubjected to a further processing step—for example, the cut length isbonded to a container liner under manufacture.

The support itself may be in two parts, having an auxiliary discconnectable co-axially to the support and selectively releasabletherefrom. For example, an electromagnet mounted on the support orauxiliary disc may be provided to allow such connection and release. Theauxiliary disc preferably has a diameter no greater than that of thesupport, but may be smaller. In the latter case, it is advantageous forthe area of the auxiliary disc to be substantially the same as that ofthe tube, when opened out.

The tube cutter preferably acts on the tube at a position adjacent thesupport when in its second position. Such a tube cutter may comprise atleast one blade arranged for rotational movement about the tube, so asto effect a circumferential cut through the tube. For a two partsupport, the cutter preferably acts to cut the tube between the twoparts. Either an externally-acting cutter or a cutter arranged betweenthe two parts of the support, to act internally of the tube, may beemployed.

A gripper mechanism may be mounted for vertical movement on the carrier,which gripper mechanism is arranged for gripping an end portion of thetube and then to draw the tube over the support prior to the cutting ofthe tube. Such a gripper mechanism may have an annulus surrounding thesupport and provided with gripping fingers or other clamps, to grasp theend portion of the tube.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only, one specific embodiment of tube handlingapparatus constructed and arranged in accordance with the presentinvention and configured to perform a method of this invention, andcertain modifications thereof, will now be described in detail,reference being made to the accompanying drawings, in which:

FIG. 1 is a diagrammatic end view on the embodiment of apparatus, withthat apparatus in an initial setting ready to perform a tube handlingcycle, of cutting a length of tube from a web and then bonding the cutlength to a sheet of plastic material around an opening therein, so asthereby to form an access pipe for a container liner being manufacturedfrom said sheet;

FIGS. 2 to 9 show successive steps in the tube handling cycle performedby the apparatus of FIG. 1;

FIG. 10 is an isometric view of the tube support shown in FIGS. 1 to 9,and also of a tube-cutter, in a first position;

FIG. 11 is a view similar to that of FIG. 10 but in a second position;

FIGS. 12 and 13 are plan views on the assemblies of FIGS. 10 and 11,respectively;

FIG. 14 is a side view on part of the apparatus shown in FIGS. 1 to 9;

FIG. 15 is a detail view on the tube support and gripping arrangementused in the apparatus of FIG. 14;

FIG. 16 is a plan view on a modified cutter arrangement, provided withinthe tube support;

FIG. 17 is a perspective view on the cutter arrangement of FIG. 16; and

FIG. 18 diagrammatically illustrates the first, second and thirdpositions of the support.

DETAILED DESCRIPTION OF THE INVENTION

Referring initially to FIG. 1, there is shown the embodiment ofapparatus of this invention for performing a tube handling method, alsoof this invention. In addition, the drawings show part of apparatus formanufacturing a cargo container liner, so that an access pipe may beprovided thereon, that access pipe being formed by the tube handlingmethod described herein.

A reel 15 of folded-flat plastics material tube 16 is supported on aframe 17 having an upper work area 18, and to which the tube 16 is fedduring initial setting up of the apparatus. An overhead gantry 19extends over the frame 17 as well as the work table 20 of an automatedliner-manufacturing production line. There, a length of liner plasticstubular material is drawn out over the work table 20 in order thatvarious manufacturing processes may be performed thereon, including theattachment of a length of tube 16 to form an access pipe for a finishedcontainer liner. Apart from this step, the manufacturing process for theliner forms no part of the present invention and will not be describedin further detail here.

The gantry 19 has a track 22 along which runs a carriage 23. An endlesschain 24 is arranged alongside the track 22, passing round a pulley 25at one end of the track and round a drive wheel on the output shaft ofan electric motor 26 at the other end. The carriage 23 is coupled to thechain so as to be moved along the track on operation of the motor,between a first position (FIG. 1) above the frame 17 and a secondposition (FIG. 6) above the work table 20, at appropriate times duringthe performance of the method.

The carriage 23 includes a platform 27 suspended below the track 22 bybars 28, the platform slidably mounting a pair of arms 29 and 30, whichalso pass through guides 31 and 32 provided in the carriage, at thelevel of the track 22. The two arms 29, 30 have respective toothed racks33, 34, each engaged with a respective driving pinion provided on theoutput shaft of an individually controllable motor 35, 36 mounted on theplatform 27. The lower ends of the arms 29, 30 are provided witharticulated links 37, 38 coupling the arms to a disc-shaped support 39,described in more detail below, at diametrically opposed locations. Byappropriate driving of the motors 35, 36, the support 39 may be movedbetween an inclined (first) position shown in FIGS. 1, 14 and 15 and ahorizontal (second) position shown in FIGS. 4 and 9.

The arms 29, 30 together with guides 31, 32 and racks 33, 34 comprise acarrier for the support 39. The carriage 23, bars 28 and platform 27carrying the motors 35, 36 and guides 31, 32 together comprise asub-frame supporting the carrier and movable between a loading position(FIGS. 1 to 5) and a discharge position (FIGS. 6 to 8).

A gripper assembly 41, comprising an annulus 42 from which depends aplurality of gripper fingers 43, is suspended below the carriage 23 onlegs 44, for vertical movement. The annulus is of a greater diameterthan the support 39 and platform 27, so that the annulus may movethereover, a suitable drive arrangement including motors 45 engaged withthe respective legs 44 being provided on the carriage to effect suchvertical movement. Further actuators (not shown) for the fingers 43 areprovided so that the fingers may be opened and closed, when required.

The support 39 has a main upper part 47 and an auxiliary lower part 48,both parts being disc-shaped and having central aperture 49 extendingtherethrough. An electromagnet 48A is provided in an upstand of thelower part 48 so that when energized the upper part 47 is held securelyto the lower part, but when not energized, the upper part may be movedaway from the lower part. Means (not shown) are provided to ensureaccurate co-axial alignment between the upper and lower parts 47 and 48,when held together by the electromagnet 48A. Such means may compriseinter-engaging pegs and sockets on the two parts, with those pegs andsockets being given appropriate leads to facilitate inter-engagement.Alternatively, a servo-drive arrangement may be used to obtainregistration between the-two parts.

The diameter of the upper part 47 is greater than the internal diameterof the tube 16 with which the apparatus is to be used, so that when thetube overlies the upper part 47 with that part in a radial plane of thetube, the tube is radially stretched over the upper part. However, bysufficiently inclining the support 39 at an angle to the axis of thetube, as shown for example in FIG. 3, the effective (projected) area ofthe upper part may be reduced to that of the opened-out tube, so thatthe tube 16 may easily be drawn from the reel 15 by the gripper assembly41 to pass over the support, without the tube being stretched.

The diameter of the lower part 48 in general should not be greater thanthe diameter of the upper part 47, and in the illustrated embodiment isessentially of the same diameter. The diameter of the lower part couldbe slightly smaller than that of the upper part and possibly evensmaller than the diameter of the tube, when opened out. In this case,the tube will not be stretched when it overlies the lower part 48 sothat there will be no tendency for the free end of the tube, followingsevering of the drawn length and which projects above the lower partresiliently to curl inwardly. In turn, this assists the gripping of thefree end of the tube, by the gripper fingers 43.

The work area 18 of the frame 17 supports a pair of concentric rails 51,with the diameter of the inner rail being sufficiently large toaccommodate the support 39. A pair of carriers 52 are mounted on therails 51 in a diametrically opposed relationship, each carrier having acutting blade 53 slidably mounted thereon for movement in the radialdirection. When the blades 53 are moved radially inwardly and thecarriers moved around the rails 51, a circumferential cut will be madearound tube 16 between the two parts 47,48 of the support 39, whenlocated horizontally within the inner rail 51.

Four rams 55 (FIGS. 10 to 13) are equi-spaced around the inner rail 51,each ram acting in the respective radial direction. Each ram has a clampjaw 56 at its radially inner end, whereby the lower part 48 of thesupport 39 may be clamped thereby, following the positioning of thesupport 39 on the work area 18 as shown in FIG. 11. Further, each clampjaw 56 is provided with a movable finger 57 the radially inner end ofwhich may be moved generally vertically. For this purpose, anelectromagnetic actuator may be provided on the jaw 56, to cause thefinger to rock about the horizontal axis.

The operation of the apparatus will now be described. A reel 15 offolded-flat plastics material tube 16 is placed on rollers 59 providedat the base of the frame 17 and the tube is then fed round a jockeyroller 60 and through a roller nip 61 to the work area 18 at the top ofthe frame 17, the tube being opened out into a generally circular form.During initial setting up, the motors 35, 36 are driven so that thesupport 39 (with the upper and lower parts 47,48 thereof securedtogether) lies at the angle shown in FIGS. 1, 2 and 14 and so has aneffective area, projected in the vertical direction, of about the samearea as (but not greater than) that of the opened-out tube. The gripperassembly 41 is lowered to the work area 18 and the fingers 43 operatedso as to grip the upper marginal region of the tube 16. This initialsetting of the apparatus and tube is as shown in FIGS. 2, 14 and 15,FIG. 1 showing the fingers in their open position, ready for grippingthe tube.

The gripper assembly 41 is then pulled upwardly (FIG. 3) by motors 45,drawing the tube 16 over the inclined support 39. A suitable length oftube for the required access pipe of the liner is drawn from the reel15, by controlling the upward movement of the gripper assembly 41. Themotors 35 and 36 are appropriately driven to lower the support 39 downto the work area 18 of the frame 17 and, as the support reaches thatarea, the angle of the support is moved to and then slightly beyond thehorizontal position by a few degrees, before being pulled back to thehorizontal position (FIG. 4).

FIG. 18 diagrammatically shows the support in its first position I, itssecond position II and its third position III.

Once horizontal, the support 39 is clamped in that position by drivingthe rams 55 to engage the clamp jaws 56 with the lower part 48 of thesupport. The tube 16 is then cut between the upper and lower parts ofthe support 39, by moving the blades 53 radially inwardly and drivingthe two carriers 52 for at least 180°, so that the blades 53 perform acircumferential cutting operation around the tube 16. This severs thepart of the tube drawn over the support from the main part of the web ofthe tube (FIG. 5). If stretching of the tube over the lower part of thesupport occurs, the cut free edge region of the tube will tend to springinwardly. The movable fingers 57 on the clamp jaws 56 are operated so asto engage behind that cut edge and hold it against further inwardmovement.

The electromagnet of the support is de-energised and the upper part 47is lifted slightly and then moved away from the lower part, byhorizontal movement of the carriage 23 until the upper part overlies thework table 20 of the liner manufacturing production line (FIG. 6). Theshort length of tube 16 below the upper part 47 of the support is ableto relax and so curls inwardly to form a flange 63, with the adjacenttube extending over the upper part 47 of the support being stretched.

In FIG. 7, the upper part 47 of the support is shown lowered by themotors 35, 36 to engage a plastics material liner being manufactured onthe work table 20. A thermal welding arrangement such as an annularheater 47A is included in the upper part 47 of the support 39, but couldinstead be incorporated within the work table 20, whereby the flange 63is thermally welded to the liner on the work table. Other bondingtechnique could be used such as chemical welding or use of an adhesive.

As shown in FIG. 6, an annular blade 47B may be mounted on the undersurface of the upper part 47 of the support, to cut an opening throughthe plastics material liner being manufactured on the work table 20, theflange being welded to that liner around the opening.

Once the welding has been completed, the upper part of the support israised and tilted, as shown in FIG. 8, leaving the tube 16 bonded to theliner, so as to form an access pipe for that liner. In view of theflexible nature of the plastics material, the access pipe may fall awayfrom the support 39, whereafter the carriage 23 is moved back to overliethe frame 17 and be re-engaged with the lower part 48 of the support(FIG. 9). The rams 55 are moved slightly outwardly so that the fingers57 may pull the cut edge of the tube outwardly, ready for re-engagementby the gripper assembly 41. Following the lowering of the gripperassembly 41 and the gripping of the cut edge by the gripper assemblyfingers 43, the clamping jaw fingers are rocked upwardly to come free ofthe cut edge and the clamp jaws 56 are moved radially outwardly towardsthe inner rail 51. The support is moved back to its tilted firstposition, returning the apparatus to the condition shown in FIG. 1,ready for the performance once more of the cycle of operation.

Referring now to FIGS. 16 and 17, there is shown an alternative cutterarrangement to replace that shown for example in FIGS. 10 to 13. Thisalternative cutter arrangement is mounted on the lower part 48 of thesupport 39 and operates outwardly, from within the lower part. In thisway, external cutter blades on the work area 18 can be eliminated.

A spider 65 is rotatably mounted on the lower part 48 of the support 39,closely to overlie that support. The spider has four arms 66 each ofwhich carries at its radially outer end an arcuate bar 67. At each ofthe two ends of each bar 67 there is mounted a respective solenoidactuator 68, the armature 69 of which projects radially outwardly.Releasably mounted on each armature 69 is a respective replaceablecutter blade 70, whereby energisation of each solenoid causes all of thecutter blades 70 simultaneously to move radially outwardly, beyond theouter periphery of the lower part 48 of the support 39.

An annulus 72 is mounted on four pillars 73 on the lower part 48 andserves to connect to the upper part 47 of the support 39, for example bymeans of further electromagnets, as discussed above. Further, the upperpart 47 may include a registration ring (not shown) to ensure correctaxial alignment of the upper and lower parts 47 and 48.

As shown in the drawings, each arm 66 is cut away adjacent itsrespective bar 67, to permit the partial accommodation of a pillar 73.Thus, the spider 65 may move through slightly less than 90degs, themovement being limited by the pillars 73. A drive mechanism (not shown)may be provided for the spider, such as a stepper motor. Power for sucha motor and also for the solenoid 68 may be supplied from the upper partof the support 39, when the upper and lower parts are connectedtogether.

In this arrangement, the diameter of the lower part 48 advantageously issubstantially equal to, or smaller than, the diameter of the tube, whenopened out. Thus, the diameter of the lower part will be less than thatof the upper part. Equi-spaced around the periphery of the lower part 48are eight upstanding tabs 74, arranged so as not to be contacted by theprojecting blades of the spider. Those tabs serve to support the freeend of a tube, following the severing of a drawn length of the tube andthe subsequent removal of that drawn length, away from the lower part48. By supporting the free end of the tube, the engagement of that freeend by the gripper fingers 43 is much facilitated. The tabs 74 could bemounted for movement generally in a radial direction, to offering of thefree end of the tube to gripper fingers 43.

What is claimed is:
 1. Apparatus for handling a tube of flexibleplastics material drawn and then cut from a web thereof, said apparatuscomprising a disc-shaped support having an axis and being of a greaterdiameter than the internal diameter of the tube and over which thematerial is drawn, and a carrier for the support, said support beingmounted on the carrier for movement between a first position where thesupport lies at an angle to a radial plane of the tube to permit drawingof the tube thereover and a second position where the support liessubstantially in a radial plane of the tube within a part thereof, saidpart of the tube becoming stretched over the support so as to be heldthereby on movement of the support to its second position.
 2. Apparatusas claimed in claim 1, wherein the carrier for the support comprises atleast two arms connected to and spaced around the support, the armsbeing independently movable to effect movement of the support betweenits said positions.
 3. Apparatus as claimed in claim 1, wherein thesupport is mounted on the carrier for movement to a third positioninclined at an angle to the radial plane of the tube and beyond thesecond position with respect to the first position.
 4. Apparatus asclaimed in claim 1, wherein the support includes one of thermal weldingmeans, chemical fusion means and adhesive dispensing means, arranged toattach a supported tube to another plastic material located at theunloading position of the support.
 5. Apparatus as claimed in claim 4,wherein the support includes a cutter which cuts an opening in a sheetof a plastics material located at the unloading position of the supportand to which said plastics material the tube is bonded, around the cutopening.
 6. Apparatus as claimed in claim 1, wherein the carrier ismounted on a sub-frame, and the sub-frame is arranged to move thesupport from a loading position where the tube is drawn over thesupport, to a discharge position and back to the loading position. 7.Apparatus as claimed in claim 6, and further comprising a grippermechanism associated with the sub-frame and arranged to grip the freeend of a web of tube material and draw the free end over and beyond thesupport such that the support is located at a required position withinthe tube, spaced by a pre-set distance from the free end of the tubematerial, prior to movement of the support to its second position andthe cutting of the tube from the web thereof.
 8. Apparatus as claimed inclaim 6, wherein a tube cutter is provided at the loading position, tocut off a length of the tube drawn over the support from a web of thetube material.
 9. Apparatus as claimed in claim 8, wherein the tubecutter acts adjacent the support when in its second position, on a partof the tube which has been stretched by the support moving to its saidsecond position.
 10. Apparatus as claimed in claim 9, wherein the tubecutter comprises at least one blade arranged for rotational movementabout the axis of the support when in its second position, adjacent saidsupport.
 11. Apparatus as claimed in claim 9, wherein the tube cuttercomprises at least one blade carried within the support and projectableoutwardly thereof, the at least one blade being mounted for rotationalmovement about the axis of the support.
 12. Apparatus as claimed inclaim 8, wherein the support comprises a disc-shaped main part and adisc-shaped auxiliary part connectable co-axially to the main part ofthe support and selectively releasable therefrom, the auxiliary parthaving a diameter no greater than that of the main part of the support.13. Apparatus as claimed in claim 12, wherein electromagnetic means isprovided on one of the main and auxiliary parts, selectively to holdtogether the main and auxiliary part of the support.
 14. Apparatus asclaimed in claim 12, wherein a clamp is provided for the auxiliary part,to maintain the position of the auxiliary part when released from themain part of the support.
 15. Apparatus as claimed in claim 12, whereinthe cutter acts on the web between the main and the auxiliary parts ofthe support, and the auxiliary part is released from the main part ofthe support when the main part is to be moved from the loading position,so leaving the free end portion of the web of tube material over-lyingthe auxiliary part.
 16. A method of handling a tube of flexible plasticsmaterial using a disc-shaped support having an axis and being of agreater diameter than the internal diameter of the tube when opened outand being adjustably mounted on a carrier for movement between a firstposition where the support lies at an angle to a radial plane of thetube and a second position where the support lies substantially in aradial plane of the tube, in which method the support is disposed at itssaid first position, a length of the tube is drawn over the support froma web thereof, the support is moved to its second position so as tostretch over the support that part of the tube in which is located thesupport, whereby said part of the tube is held thereby, and the drawnlength of the tube is cut from the web adjacent the support.
 17. Amethod as claimed in claim 16, in which the support is moveable to athird position disposed at an angle to the radial plane and beyond thesecond position with respect to the first position, and to which thirdposition the support is moved from the first position before moving tothe second position.
 18. A method as claimed in claim 16 in which thesupport comprises main and auxiliary parts, said auxiliary part being adisc of a diameter not greater than that of the main part, in whichmethod the auxiliary part is connected to the main part and is movedtherewith to the first position so that the tube may be drawn over themain and auxiliary parts, the main and auxiliary parts are moved to thesecond position, and then a cut to separate the drawn tube from theremainder of the web is performed between the main and auxiliary parts.19. A method as claimed in claim 18, in which the support is moveable toa third position disposed at an angle to the radial plane and beyond thesecond position with respect to the first position, and to which thirdposition the support is moved from the first position before moving tothe second position.
 20. A method as claimed in claim 18, in which thecarrier and main part are moved away from the auxiliary part to atube-discharge position following the cutting of the tube from the webthereof, the auxiliary part remaining within the end portion of the tubeweb.
 21. A method as claimed in claim 20, wherein the end portion of thetube held by the main part is bonded to another plastics sheet materialwhen the tube is moved by the main part of the support to thetube-discharge position.